<form method="get" id="searchform" action="<?php home_url(); ?>/">
<input type="text" value="<?php if(isset($s)) { echo $s; } else { echo "Search..."; } ?>" name="s" id="s" onfocus="if (this.value == 'Search...') {this.value = '';}" onblur="if (this.value == '') {this.value = 'Search...';}" />
<input type="submit" id="searchsubmit" value="Search" />
</form>